Cut-out for incandescent electric lamps and similar devices



Feb. 6, 1934. E. FRIEDERICH Er Al. 1,946,279

CUT-OUT FOR INCANDESCENT ELECTRIC LAMPS AND SIMILAR DEVICES Filed Aug. 9, 1929 JAA/'EN TUBE: SVTHE'R SEHERA/rm Ems T Rza-'355255Z Tiana Arroz-1m52- PATENT OFFICE CUT-OUT FOR INCANDESCENT ELECTRIC LAMPS AND SIMILAR DEVICES unisi rriedevricn and lBei-lin-Charlottenburg, Germany,

Gnther scliermann, assignors .to

General Electric Company. a corporation of New York application August 9. 1929, serial No. 384,124. and in Germany August 17, 1928 3 maims.

Our invention relates to electric incandescent lamps and similar electrical devices which comprise a glass container having sealed therein a. filament or other electric energy translation element and a base to which is attached leading-in conductors. More particularly, our invention relates to devices of that character which are adapted to be arranged in a group and connected in series. The system may be alternating 'current or direct current, and it is desirable that means be provided so that upon the failure of one or more of the lamps, that lamp or lamps will be cut out of the circuit and the remainder of the lamps of the group will continue to operate.

According to our invention, from one standpoint, the cut-out means is embodied in the base and comprises a so-called shunt resistance material which is disposed between the metallic shell and metallic center contact of the base. The material is of such character that it breaks down when there is an over voltage across the lamp terminals caused, for instance, by the failure of the rilament. From another standpoint, an important feature of our invention is to constitute the elements between which the shunt resistance material is disposed, for instance, the shell and center contact, of metal such that with the shunt resistance material there will be an action correspending to that'in so-called dry rectirlers and which will normally prevent the passage of current. In direct current systems it is necessary to prevent passage of current in one direction, but in alternating current systems, passage of current in either direction must be prevented so' that, for direct current systems, on1y one of the terminal elements need be of the metal which, with the shunt resistance material, will have the property of preventing passage of the current at normal voltages. Various other features and advantages of our invention will appear from the description which follows of species'thereoi and from the accompanying drawing.

In the drawing Fig. 1 is a partial elevation, partly in vertical section, of a base comprising our invention; Fig. 2 is a top plan view thereof; and Fig. 3 is a vertical section of'a modification.

The base shown in Figs. 1 and 3 comprises the metallic shell 10, the metallic center contact 11 and the intermediate insulation 12, which may be glass, porcelain or similar substance. in wires, which are not shown, connect the shell 10 and center contact'll with the lamp iilament which is also not shown. Packed in radial grooves formed in the outer surface o! the insulation 12 are the shunt resistors 1.3. TheseA resistors may consist of various materials which have the property of being non-conductive below a certain volt- The lead-v age. Copper iodide or copper oxide are examples of such materials. A paste may be made of these materials using shellac as a binding medium which may be then applied to .the grooves inthe insulation 12. After evaporation of the binding medium, the copper iodide or copper oixide will be hardened and will stick securely in the said grooves. lf desired, easily reducible salts such as the acetate o! lead or copper may be incorl -porated. When the break down occurs, these will be reduced and a metallic conductive connection will be established between the metal parts of the base. However, this is not essential. We prefer that the contact 11 and shell 10 be of metals, for example, lead or silver, which we term plumbic materials and which will act with the shunt resistance to prevent the passage of current at normal voltage in both direction, the action being similar to that in so-called dry rectiers. As shown in the drawing, it is preferred to coat the ordinary brass metal contact and shell with lead or silver coatings 14-15 which are in direct contact with the shunt resistors 13.

In the commotion shown in Fig. 3, .a hood 16 is placed over the center contact 11 as by soldering or welding. Intex-posed between the lower edge of the said hood 16 and the shell 10, is a ring 17 constituting the shunt resistor. The hood 16 and the shell are preferably composed oi, or, as shown, are coated with lead or silver 18--19. It is preferred that theshunt resistors 13 comprise a core 20 of lead or other easily fusible metal having the coating of the copper iodide or copper oxide base. In this way the break down of the shunt resistor will cause thehood and shell to be fused together.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. In an electric lamp, the combination of plumbic surfaced terminal members separated and in electrical contact with a shunt resisto containing a copper compound.

2. A base for electric lamps comprising a metallic center contact and a shell separated by an insulator and, a shunt resistor material carried in grooves in said insulator and in electrical contact with said center contact and shell.

3. In an electric lamp, the combination of plumbic surfaced terminal members separated and in electrical contact with a shunt resistor, said resistor comprising a body of normally non conductive material which becomes a conductor and allows the passage or current therethrough above a certain voltage.

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